docs: def set_cells(self, cells_location):
          """
          Set self.cells to function :cells in file pathname.py
          :param cells_location: cells location, format 'pathname.py:cells'
          :return:
          """
  
          if ':' in cells_location:
              pathname, func_name = cells_location.split(':')
          else:
              pathname = cells_location
              func_name = 'cells'
  
          check_isfile(pathname)
  
          try:
              self.cells = get_func(func_name, pathname)
          except SyntaxError as e:
              fatal(traceback.format_exc(limit=1))
  
          return pathname, func_name